Special Issue on COVID-19 Aerosol Drivers, Impacts and Mitigation (IX)

Hayoung Park1, Sujong Jeong  1, Ja-Ho Koo2, Sojung Sim1, Yeon Bae1, Yeonsoo Kim1, Chaerin Park1, Jeongyeon Bang1 

1 Department of Environmental Planning, Graduate School of Environmental Studies, Seoul National University, Seoul, Korea
2 Department of Atmospheric Sciences, Yonsei University, Seoul, Korea

Received: July 5, 2020
Revised: September 23, 2020
Accepted: September 29, 2020

 Copyright The Author(s). This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are cited.

Download Citation: ||https://doi.org/10.4209/aaqr.2020.07.0376  

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Cite this article:

Park, H., Jeong, S., Koo, J.H., Sim, S., Bae, Y., Kim, Y., Park, C., Bang, J. (2021). Lessons from COVID-19 and Seoul: Effects of Reduced Human Activity from Social Distancing on Urban CO2 Concentration and Air Quality. Aerosol Air Qual. Res. 21, 200376. https://doi.org/10.4209/aaqr.2020.07.0376


  • Due to COVID-19, human activity in Seoul reduces in 2020 compared to previous year.
  • Urban enhancements of CO, NO2, and CO2 in Seoul decrease while background CO2 rises.
  • Decline in CO:CO2 and NO2:CO2 ratios in 2020 show improvement in air quality.


Social restriction in cities to curb infection rates of COVID-19 has become an opportunity to investigate the relationship between humans and the urban atmosphere. We evaluate the impact of the decline in human activities as a result of social distancing on the urban CO2 concentrations and air quality in Seoul during February and March of 2020 compared to 2019. Due to the reduction in human activity in 2020, local measurements of CO and NO2 show a decrease in background concentration (up to –11.9% and –41.7%, respectively) and urban enhancement (up to –16.7% and –38.1%, respectively) compared to the previous year. In contrast, the background concentration of CO2 increases by 3.9% in 2020. Ratios of CO:CO2 and NO2:CO2 also show a decrease in 2020 compared to the previous year, signaling an improvement in the urban air quality of Seoul. Moreover, the insignificant change in wind speed and wind direction during the months of February and March 2020 compared to 2019 implies that CO2, CO, and NO2 concentrations have not been influenced by meteorological conditions, but mainly by changes in emissions from decreased human activity. Despite the rise in background CO2 concentration, urban contributions of CO2 show a decline of –12.6%, indicating that cities with high emissions have the potential to reduce urban CO2 enhancements and air pollutant concentrations, and ultimately impact the global atmosphere.

Keywords: COVID-19, Social distancing, Urban emissions, Air quality

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